Antenna



Feb 4 M. A. EDWARDS EI'AL 79 I ANTENNA Filed March 27,1943 I 3Sheets-Shet 1 0 '1 1F W W; 4T o 1 A E" J 0 o 0 Q o L Q q s O V 6 o 0 a/8 o I I 8 3 8 Y Inventors. Martm AEdwards.

Hu hMOQIe,

Gerald A.Hoy 0, b x/ HW y Their Attorney.

Feb. 11, 1947. M. A. EDWARDS ET AL 2,415,679

ANTENNA Filed March 27, 1943 3 Sheets-Sheet 2 Inventors: MartinAEdwards,

Hugh M.O g|e,. Gerald Afioyt,

fia fi/fjwmwt v y. Their Attorney.

Feb. 11, 1947.

M. A. EDWARDS ETAL ANTENNA 3 Sheets-Sheet 3 Inventors Martin A.Edwards,

Their Attorney w H M A E H e P an-a r m G Patented Feb. 11, 1947 angersANTENNA Martin A. Edwards, Scotia, and Hugh M. Ogle and Gerald A. Hoyt,Schenectady, N. Y., assignors to General Electric Company, a corporationof New York Application March 27, 1943, Serial No. 480,892

3 Claims.

The present invention relates to directional antennas of the type knownas scanners or spinners, and is particularly concerned with anarrangement for preventing shiftin of the directive axis of the antennadue to the pitch or roll of the support (e. g. a ship) on which theantenna is carried. Such antennas are primarily used with radio locatingequipment for scanning the horizon or zones at a small elevation fromthe horizon to obtain information as to the location of remote objects.

The object of our invention is to provide a directive antenna with animproved arrangement for neutralizing the effect of pitch or roll.

The novel features which we believe to be characteristic of ourinvention are set forth with particularity in the appended claims. Ourinvention itself, however, both as to its organization and method ofoperation, together with further objects and advantages thereof, maybest be understood by reference to the following description taken inconnection with the accompanying drawings in which Fig. 1 is a rearelevation of an an tenna embodying our invention; Fig, 2 is a sideelevation; Fig. 3 is a diagram of the elevation control; Fig. 4 is adiagram of the azimuth control; Fig. 5 is a top plan view of thegyroscope; and Fig. 6 is a sectional elevation of the elevation drive.

Referring to the drawings, there is shown a scanner mounted on aturntabl l journaled for rotation on a vertical axis in a base 2. Fixedon the turntable is a transmission line 3, the lower end of which isconnected to a rotating joint (not shown) at the axis of the turntableand the upper end or" which extends through a clear nce opening in aparabolic reflector 5 and terminates in a radiator 4, shown in Fig. 2.The radiator and reflector constitute an antenna having a directive axisdetermined by the relative position of the radiator and reflector. Thereflector is supported by trunnions e at the upper ends of standards 'lfixed to the turntable for tilting relative to the turntable on ahorizontal axis erpendicular to the axis of the reflector. The directiveaxis of the antenna is shifted in azimuth by rotating the turntable andin elevation by tilting the reflector relative to the turntable. Due toreflection the directive axis is shifted in elevation through twice theangle between the radiator i and the axis of the reflector.

The turntable is rotated in azimuth by a motor 8 through reductiongearing 9 which drives a pinion ID meshing with a crown gear I fixed tothe outer edge of the turntable. The position of the directive axis ofthe antenna in azimuth, which corresponds to the position of theturntable, is controlled by a generator Selsyn i2 (which may be locatedin a control box remote from the antenna) having its rotor it connectedto an A.-C. supply and optionally rotated by a motor M or a hand crankand having its stator it connected to the stator ll of a Selsyntransformer E8 on the base 2 The rotor E9 of the Selsyn transformer isdriven from the crown gear 5 l through a pinion 2G and reduction gearing2! so its position at all times corresponds to the azimuth of theantenna. Whenever the position of the rotor l9 does not exactlycorrespond to the position of the rotor E3 of the indicator Selsyn, adisplacement voltage is induced in the rotor l9 which corresponds inmagnitude with the magnitude of the displacement and in phase with thedirection of the displacement. In apparatus indicated at 22, thedisplacement voltage is converted by amplification and rectification toa 11-0. voltage varying in magnitude and polarity in accordance with themagnitude and direction of the displacement. This voltage is applied tothe fields 23 of a generator 24 which generates a voltage correspondingto its excitation in magnitude and polarity. The voltage of thegenerator 24 is applied to the motor 8, causing rotation of theturntable in the direction to reduce the displacement between the rotorsof the Selsyns l2 and l 8 so that the directive axis of the antenna ispositioned in azimuth in accordance with the generator Selsyn l2.

The directive axis of the antenna is shifted in elevation by a motor 25through reduction gearing 25 having a pinion 2'! meshing with a gearsector 28 fixed to the back of the reflector 5. The motor 25 isenergized through slip rings 29 on the turntable from a generatorsimilar to the generator 2%. The connections to the other elec tricalapparatus carried by the turntable are also made through the slip rings29. The motor also drives the stator ill of a Selsyn transformer 32through reduction gearing 33 having one half the reduction of thegearing driving the reflector so the angular position of the stator 5icorresponds to the elevation. of the directive axis of the antenna whichis shifted by twice the angle the reflector is moved. The stator 35 isjournaled in a housing fixed to a U-shaped frame 35 bolted to theturntable. Journaled in the frame 35 on a horizontal axis perpendicularto a vertical plane including the directive axis of the antenna is aframe 35 having a shaft 31 fixed to the rotor 38 of the Selsyntransformer The frame 36 is held horizontal in a plane along thedirective axis of the antenna by a gyro-scope stable vertical carried ina frame 39 pivoted to the frame 36 on a horizontal axis along thedirective axis of the antenna. The gyroscope consists of an inductionmotor having its stator fixed to the frame 39 and a rotor Allsurrounding the stator. At the lower end of the rotor is a sphericaleddy current damper 5! cooperating with a permanent magnet 42 supportedby a universal pendulous suspension 438. from the frame The magnet,which is free to swing in any direction, has a very short period and itsaverage position over an intervai of a few seconds is true vertical. Ifthe axis of the rotor dii differs from true vertical, the drag due toeddy currents in the damper 4! causes the gyroscope to precess towardtrue vertical. So long as the gyroscope is in true vertical, the frameit is horizontal in a vertical plane along the directive axis of theantenna although the frame may be inclined in a perpendicular Verticalplane.

The elevation of the antenna is controlled by a Selsyn 43 (which may belocated in'a control box remote from the antenna) having a stator Mconnected to the stator 34 of the Selsyn transformer t2 and a rotor 45connected to an A.-C. supply. lhe rotor 65 is positioned to the desiredelevation angle in any suitable manner, for example by a hand crank 45.Whenever the position of the rotor 38 of the Selsyn transformer does notcorrespond to the position of the rotor 45, a displacement voltage isinduced which corresponds in magnitude to the magnitude of thedisplacement and in phase to the direction of the dis placement. Inapparatus indicated at M, the displacement voltage is amplified andrectified and supplied to the fields 43 of the generator 32) whichgenerates a control voltage for the motor 25 of magnitude and polaritysuch that the motor drives the stator 3! (and the antenna) in thedirection to decrease the displacement.

In the use of the antenna, the base 2 may be fastened to a support, suchas a platform on a ship, and the control box, containing the Selsyns i2and 43, the apparatus 22 and 47, and the generators 24 and 353 may belocated at some convenient point remote from the antenna. When used on aship, the platform supporting the antenna is usually located at as greata height as possible so radio waves along the directive axis of theantenna will encounter a minimum of obstruction. Since the direction inwhich the antenna is pointed is indicated by the Selsyns l2 and $3, thecontrol box is usually located at the place at which this information isused.

The operator, by the hand crank E5 or motor it, determines the positionof the directive axis of the antenna in azimuth and by the hand crank d5determines the position of the directive axis of the antenna inelevation. Through the displacement voltages induced in the Selsyntransformers l8 and 32, the voltages are generated by generators 2 and3% of magnitude and polarity such as to cause the motors 8 and 25 toshift the directive axis of the antenna in azimuth by rotating theturntable l and in elevation by tilting the reflector 5 to a positoncorresponding to the azimuth elevation indicated by the positions of thehand cranks l5 and d6. As the ship pitches and rolls, the components ofthe pitch and roll along the directive axis of the antenna arecompensated by the gyroscope 33 which holds the frame horizontal in avertical plane along the directive axis of the antenna. This holds therotor 38 of the Selsyn transformer 32 in a horizontal position andcauses the stator 3! to assume a position relative to the rotor 38corresponding to the relative position of the rotor and the stator. 4The directive axis of the antenna, which corresponds to the position ofthe stator 3 I, is accordingly held at the elevation angle correspondingto the setting of the hand crank 45. Since the elevation of thedirective axis of the antenna is with reference to the horizontal framethe elevation is not affected by tilting of the base due to pitch orroll. The pitch and roll are compensated only along the directive axisof the antenna. When the directive axis is lengthwise of the ship, thecompensation is solely for pitch of the ship since the roll of the shipdoes not affect the azimuth or elevation of the directive axis. When thedirective axis is crosswise of the ship, the compensation is solely forroll since pitch does not affect the azimuth or elevation of thedirective axis. At intermediate points, the compensation is solely forthe components of pitch and roll along the directive axis since thecomponents of pitch and roll at right angles to the directive axis donot affect the azimuth or elevation of the directive axis.

While we have shown particular embodiments of our invention, it will beunderstood that many modifications may be made without departing fromthe spirit thereof, and w contemplate by the appended claims to coverany such modifications as fall within the true spirit and scope of ourinvention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. In combination, a directional antenna, means supporting the antennafor tilting about a horizontal axis perpendicular to its directive axis,a turntable rotatable on a vertical axis carrying said supporting means,a frame on the turntable pivoted on a horizontal axis perpendicular to avertical plane including said directive axis, a gyroscope on said frameholding said frame horizontal in a direction along said directive axis,and means responsive to the angle between said frame and the directiveaxis of the antenna for rotating the antenna on its horizontal axis tomaintain said angle at a predetermined value.

2. In combination,

a directional antenna,

means supporting the antenna for tilting about a horizontal axisperpendicular to its directive axis, a frame pivoted on a horizontalaxis perpendicular to a vertical plane including said directive axis, agyroscope on said frame holding said frame horizontal in a directionalong said directive axis, a motor on the turntable, a d ive from themotor for rotating the antenna about its horizontal axis, angleresponsive means on the turntable having relatively movable parts one ofwhich is connected to said frame and the other of which is moved inaccordance with the position of the antenna, and means responsive tochanges in the relative position of said parts from a predeterminedposition for generating a control voltage for the motor causing rotationof the antenna returning said parts to said predetermined position.

3. In combination, a directional antenna for mounting on a supportsubject to pitch and roll, drives for shifting the directive axis of theantenna in azimuth and elevation relative to the support, a framejournaled on the support on an axis perpendicular to the plane: of theazimuth and elevation of the directive axis of the antenna relative tothe support, a stable vertical for holding the frame horizontal in aplane perpendicular to said first plane, and means responsive to theelevation angle in said first plane between the directive axis of theantenna and the frame for controlling the elevation drive to maintainsaid angle at a predetermined value.

MARTIN A. EDWARDS. HUGH M. OGLE. GERALD A. HOYT.

REFERENCES CITED The following references are of record in the file ofthis patent:

5 UNITED STATES PATENTS Number Name Date 1,525,783 Trenor Feb. 10, 19252,288,102 Meredith June 30, 1942 2,315,755 Warner Apr. 6, 43

